Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating activities
Net income	$ 4,807	$ 3,750	$ 3,843
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized (gains) losses on financial instruments	(114)	180	(145)
Other-than-temporary impairment losses recognized in income	47	26	33
Loss on extinguishment of debt	2	11	282
Loss on disposal of assets	3	13	15
Deferred income taxes	81	91	(1,272)
Amortization, net of accretion	986	1,008	780
Depreciation expense	147	124	111
Share-based compensation	294	226	170
Changes in operating assets and liabilities:
Receivables, net	(1,053)	(695)	(22)
Other invested assets	(48)	(1)	(36)
Other assets	(170)	(26)	(629)
Policy liabilities	1,826	(1,059)	732
Unearned income	115	(36)	(120)
Accounts payable and accrued expenses	(593)	122	922
Other liabilities	148	(25)	(120)
Income taxes	(325)	323	(194)
Other, net	(92)	(205)	(165)
Net cash provided by operating activities	6,061	3,827	4,185
Investing activities
Purchases of fixed maturity securities	(10,487)	(8,244)	(9,795)
Proceeds from fixed maturity securities:
Sales	5,914	6,442	7,932
Maturities, calls and redemptions	2,437	1,938	1,848
Purchases of equity securities	(11,825)	(896)	(5,416)
Proceeds from sales of equity securities	12,364	2,809	3,463
Purchases of other invested assets	(642)	(531)	(1,164)
Proceeds from sales of other invested assets	320	411	219
Changes in collateral and settlement of non-hedging derivatives	0	0	65
Changes in securities lending collateral	254	(149)	625
Purchases of subsidiaries, net of cash acquired	0	(1,760)	(2,080)
Purchases of property and equipment	(1,077)	(1,208)	(791)
Other, net	(50)	(71)	12
Net cash used in investing activities	(2,792)	(1,259)	(5,082)
Financing activities
Net (repayments of) proceeds from commercial paper borrowings	(297)	(107)	175
Proceeds from long-term borrowings	2,473	835	5,458
Repayments of long-term borrowings	(1,123)	(1,684)	(2,815)
Proceeds from short-term borrowings	7,590	9,120	5,835
Repayments of short-term borrowings	(8,035)	(9,250)	(5,000)
Changes in securities lending payable	(254)	150	(625)
Changes in bank overdrafts	(169)	(210)	71
Premiums paid on equity call options	(1)	0
Proceeds from sale of put options	0	1	1
Proceeds from issuance of common stock under Equity Units stock purchase agreements	0	1,250	0
Repurchase and retirement of common stock	(1,701)	(1,685)	(1,998)
Change in collateral and settlements of debt-related derivatives	(34)	23	(149)
Cash dividends	(818)	(776)	(705)
Proceeds from issuance of common stock under employee stock plans	187	173	225
Taxes paid through withholding of common stock under employee stock plans	(84)	(81)	(46)
Net cash (used in) provided by financing activities	(2,266)	(2,241)	427
Effect of foreign exchange rates on cash and cash equivalents	0	(2)	4
Change in cash and cash equivalents	1,003	325	(466)
Cash and cash equivalents at beginning of year	3,934	3,609	4,075
Cash and cash equivalents at end of year	$ 4,937	$ 3,934	$ 3,609